Endless sieve belt draining device for paper machines

ABSTRACT

A draining device for a paper making machine including a longitudinal sieve which carries a slurry of paper material, a rotatable draining roller, at least one further roller, a pair of register rollers disposed with one on each side of the draining roller, and an endless sieve belt. The draining roller has a sieve-type outer surface. The endless sieve belt extends over the draining roller and the further roller and moves over these rollers at the same linear velocity as the longitudinal sieve. The endless sieve draining belt extends approximately parallel to the longitudinal sieve between the register rollers.

United States Patent 1191 Holz 1 51 June 25, 1974 ENDLESS SIEVE BELT DRAINING DEVICE FOR PAPER MACHINES [75] Inventor: Emil Holz, Eningen, Wurttenberg,

Germany 22 Filed: June 30,1972

21 App]. No.: 268,103

[30] Foreign Application Priority Data 162/351, 208, 203, 373, DIG. l, 211, 217, 297, 313, 314, 348, 363, 364, 367; 210/400, 401, DIG. 3; 74/240, 241

[56] References Cited UNITED STATES PATENTS 483,329 8/1892 Reynolds 162/373 2,141,393 12/1938 Hutchins 162/303 2,627,789 2/1953 Campbell 162/373 2,881,678 4/1959 Thomas 162/351 X 3,445,003 5/1969 Paccione 210/401 FOREIGN PATENTS OR APPLICATIONS 690,702 7/1964 Canada 210/DIG. 3 749,321 12/1966 Canada 210/400 Primary ExaminerS. Leon Bashore Assistant Examiner-Richard V. Fisher Attorney, Agent, or Firm-Spencer & Kaye [5 7] ABSTRACT A draining device for a paper making machine including a longitudinal sieve which carries a slurry of paper material, a rotatable draining roller, at least one further roller, a pair of register rollers disposed with one on each side of the draining roller, and an endless sieve belt. The draining roller has a sieve-type outer surface. The endless sieve belt extends over the draining roller and the further roller and moves over these rollers at the same linear velocity as the longitudinal sieve. The endless sieve draining belt extends approximately parallel to the longitudinal sieve between the register rollers.

22 Claims, 8 Drawing Figures PATENTEDJUNZSISH SHEET 3 BF 3 ENDLESS SIEVE BELT DRAINING DEVICE FOR PAPER MACHINES BACKGROUND OF THE INVENTION The present invention relates to a draining device, particularly for a paper making machine which includes a rotating draining roller with a sieve-type outer surface disposed above a longitudinal sieve screen which carries a slurry of paper material and moves over register rollers disposed with one on each side of the draining roller. 7

In a known draining device, the outer surface of the draining roller is provided in the form of a sieve so that the draining roller acts directly on the slurry of paper material as it passes the roller. The period of its action, however, is relatively short due to the relatively high operating speed of modern paper machines and the necessarily limited diameter of the draining roller. Moreover, the period of action can be varied only slightly by changing the diameter of the draining roller since there are practical limits to the extent to which the diameter of the draining roller can be increased. In practice, the path over which the draining roller acts on the slurry of paper material on the longitudinal sieve is 30 to 50 mm long in the direction of the longitudinal sieve, with a speed of the longitudinal sieve of from 100 to 1,000 m/min. The action time of the draining roller thus lies between 0.03 and 0.003 seconds for a path of action of 50 mm. However, because such a short action time exists in a machine with such a known draining device, a speed of 1,000 m/min is not feasible.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a draining device which permits higher speeds in paper making machines due to its longer action time.

It is a related object of the present invention to provide a draining device in which the higher speeds are achieved without a corresponding increase in the diameter of the draining roller.

It is another related object of the present invention to provide a draining device in which the surface of the endless sieve belt employed is maintained substantially wrinkle free.

These and other objects are accomplished according to the present invention by the provision of a draining device composed of an endless sieve belt which passes over the draining roller and at least one further roller and moves with a linear velocity which is equal to that of the longitudinal sieve. The endless sieve belt is partly disposed between the register rollers so that it is approximately parallel to the longitudinal sieve in the region where they cooperate.

With this construction, the diameter of the draining roller becomes almost of no significance and with an appropriate arrangement of the draining roller and the further roller, longpaths of action for the draining device can be obtained. Thus it is possible, with a simultaneous improvement in the surface regarding compression and equalization of the slurry of paper, as in the known paper machines, to obtain greater operating speeds for the paper making machines. Moreover, the space requirement for the apparatus of the present invention is no greater than that for the known draining devices.

Sieve bands arranged above the longitudinal sieve of a paper making machine are known per se, but are used to produce an entirely different effect, such as to form sheets and not as a draining device. Moreover, these known overhead sieve bands are driven in a direction opposite to the direction of movement of the longitudinal sieve and do not flatly contact the paper.

In draining devices of the type to which the invention relates, it is difficult to guide the longitudinal sieve between the register rollers so that it is level over a long path and the endless sieve belt should preferably be guided at least almost parallel to the longitudinal sieve. Therefore, it is proposed to let the endless sieve belt move approximately parallel to the longitudinal sieve from the point of contact of the draining roller with the slurry of paper material to the point of contact of the longitudinal sieve with the register roller following in the direction of movement of the longitudinal sieve. In this way there results by far the best parallel guidance of the longitudinal sieve and the endless sieve belt over the longest possible path between the register rollers. With this arrangement, the further roller for the endless sieve belt, which is disposed behind, or downstream of, the draining roller, lies directly above, or preferably behind, the second register roller and at a vertical distance above the longitudinal sieve. In the latter mentioned disposition of the further roller the endless sieve belt and the longitudinal sieve which extend beyond the area of contact of the longitudinal sieve and the register roller following in the direction of movement of the longitudinal sieve form an angle of no more than 10 therebetween. This disposition is more advisable and offers further advantages for the invention.

For the sake of, inter alia, better accessibility, the further roller which is spaced above the longitudinal sieve, rather than the draining roller, is provided with a drive which operates in synchronism with the drive of the longitudinal sieve, the further roller being spaced above the longitudinal sieve. By synchronism is meant that the further roller drive is such that the linear velocity of the endless sieve belt is equal to the linear velocity of the longitudinal sieve.

Another advantage is realized by providing the further roller of the endless sieve belt in a known manner with helical grooves starting from its center in order to prevent wrinkling of the rotating endless sieve belt.

For the same reason it is also advantageous to tension the endless sieve belt. This could be achieved by adjusting the spacing between the draining roller and the further roller. Although the distance adjustment is advantageous, it is still possible for the endless sieve belt to wrinkle in the longitudinal direction. To counteract this tendency, it is proposed according to one preferred embodiment of the present invention to provide the endless sieve belt with elastic guide belts extending longitudinally along its lateral sides. These guide belts are adopted to move in guide grooves situated at the axial ends of the draining roller and the further roller. Thus, the endless sieve belt can be tensioned longitudinally by adjusting the spacing of the two rollers from one another and/or tensioned transversely because of the engagement of the guide belts in the guide grooves. With such a positive guidance of the lateral edges of the endless sieve belt, formation therein of longitudinal wrinkles is reliably prevented.

The apparatus for effecting the distance adjustment can be of a simple construction, for example a setting gear can be provided. Another possibility for effecting the desired tensioning of the endless sieve belt in a structurally simple manner is to provide discs or wheels which are axially displaceable with respect to the draining roller and further roller under the action of springs, hydraulic or pneumatic cylinders or the like, and to provide these discs or wheels with the guide grooves.

The endless sieve belt can be tensioned particularly easily if it is a bias cut fabric, preferably a metal wire screen consisting in particular of bronze or stainless steel. For the embodiment in which the endless sieve belt is tensioned via the axial displacement of the guide belts by guide grooves, a plastic screen can also be used.

Draining devices of the type under consideration must be cleaned while in operation. This is effected by means of pipes from which a water jet or steam jet is emitted. In the known draining device however, the water jet is deflected from the draining body and its removal causes additional problems. Furthermore, care must be taken to collect the water splashed by the draining roller when it is lifted off the slurry of paper. In a preferred embodiment of the draining device according to the present invention, both problems can be solved without difficulty with a single device. It is therefore proposed to provide within the endless sieve belt a collecting trough for the water splashed from the draining roller and to have an upper portion of the col lecting trough designed to catch the water from a cleaning device for the endless sieve belt. These parts can thus be accommodated within the draining device of the present invention without creating any additional space requirement.

It has been noted that a subatmospheric pressure develops in the angular region defined between the longitudinal sieve and the endless sieve belt where the latter moves out of contact with the slurry of paper. This pressure may become so strong, under certain circumstances that the slurry of paper is sucked away from the longitudinal sieve and pulled upwardly with the endless sieve belt. This problem can be solved in different ways, for example, a pipe from which any number of steam jets are emitted can be advantageously disposed to-direct steam jets from the top through the endless sieve belt and toward the slurry of paper on the longitudinal sieve. It is also particularly recommendable to have at least the register roller which follows in the direction of movement of the longitudinal sieve after the draining roller provided with an outer surface with openings and to maintain a subatmospheric pressure at its interior. In this way, the slurry of paper is sucked against the longitudinal sieve in the critical area and further more the desired draining effect is produced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational cross-sectional view of part of a paper making machine provided with one preferred embodiment of the draining device according to the present invention.

FIG. 2 is a simplified view, on a reduced scale similar to that of FIG. 1, showing one embodimentof a tensioning device for tensioning the endless sieve belt.

FIG. 3 is a cross-sectional detail view taken along line 3-3 of FIG. 2.

FIG. 4 is a plan view of the draining device shown in FIG. 2.

FIG. 5 is a simplified view, similar to that of FIG. 2 showing another embodiment of a tensioning device for tensioning the endless sieve belt.

FIG. 6 is a cross-sectional detail view taken along line 6-6 of FIG. 5.

FIG. 7 is a plan view of the drawing device of FIG. 4.

FIG. 8 is a plan view of one embodiment of a driven roller for the endless sieve belt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a longitudinal sieve 10 on which a paper slurry 12 is placed for displacement in the direction A. The longitudinal sieve 10 moves over two register rollers 14 and 16 of which one has a rubber coating 14a and the other has apertures 16a so that it constitutes a sieve roller. The register roller 16 is arranged downstream of the register roller 14 when viewed in direction A. In the interior of register roller 16 there is a vacuum box 1612 which is connected with a pump (not shown) to maintain a continuous subatmospheric pressure therein.

The draining device according to the present invention includes a draining roller 18, a further rubber roller 20 provided with a drive (not shown) and an endless sieve belt 22 which is guided over the two rollers 18 and 20 which thus function as end rollers. End roller 20 is situated downstream of roller 18 when viewed in direction A. The draining roller 18 is provided with a sieve-type outer surface and both rollers 18 and 20 are supported on and reinforced by a tubular shaft 18a and 20a, respectively.

FIG. 1 also shows that the draining roller 18 in a preferred embodiment is disposed midway between the two register rollers 14 and 16. Moreover, the distance between the axes of the two rollers 18 and 20 for the endless sieve belt 22 is about twice that of the diameter of the draining roller 18. It has been found that these dimensions produce particularly good results. It should be understood however, that other dimensional relationships are possible within the scope of the present invention.

The rubber roller 20 has a rubber coating 20b which is provided, as shown in FIG. 8, with helical grooves 200 starting at its center and extending axially outwardly therefrom in opposite winding directions. These grooves constitute a first means for preventing the formation of wrinkles in the endless sieve belt 22.

The deflection H of the longitudinal sieve 10 between the rollers 14 and 16 determines the path of action B of the draining device of the present invention. The path B may be adjusted and made shorter or longer to adopt it to the particular operational requirements by a displacement of the draining roller 18.

As can by clearly seen in FIG. 1, the path of action B over which the endless sieve belt 22 is practically parallel with the longitudinal sieve 10 is substantially longer than the path of action that would result if only the draining roller 18 were used. To insure the parallelism between the sieve lfl along the path of action B (where the sieve 10 slopes upward), the vertical distance of the roller 18 from the sieve 10 is smaller than the vertical distance of the roller 20 from the sieve 10.

According to a preferred arrangement of the present invention, the endless sieve belt 22 forms an angle a with the longitudinal sieve 10. The angle ais substantially smaller than the exit angle B formed by the tangent to the point of the draining roller 18 leaving the surface of the paper slurry 12 and the surface of the paper slurry. For example, the angle a is preferably no more than Thus, the water drained by the sieve belt 22 forms a relatively flat trajectory D, as compared to the parabolic trajectory C, which would be formed by the draining roller 18 in the prior art devices. This constitutes a further advantage of the device of the present invention.

Since in the area where the endless sieve belt 22 departs from the paper slurry 12 a subatmospheric pressure would normally be produced, it is advisable to provide a pipe above the endless sieve belt 22 through which any number of jets of steam 30 are directed through the belt 22. As it may be observed in FIG. 1, the pipe 30 extends immediately downstream of the zone of contact between the roller 16 and the longitudinal sieve 10. The jet or jets 30 prevent the formation of a subatmospheric pressure and thereby cause the paper slurry 12 to remain with the longitudinal sieve 10.

A pipe 32 which emits any desired number of water jets 32', serves to clean the endless sieve belt 22. An advantage of the device according to the present invention is that the water jet 32' is directly sprayed against the sieve belt 22 from the pipe 32.

To collect the Water splashed by the draining roller 18 itself and the cleaning water from the pipe 32 a collecting trough assembly 34 is provided. The collecting trough assembly 34 includes a lower trough portion 34a and an upper trough assembly portion 34b for collecting the water splashed by the draining roller 18 and the pipe 32, respectively. The water splashed from the endless sieve belt 22 when the belt 22 is deflected about the rubber roller 20 is collected in a collecting trough 36.

Referring now to FIGS. 2, 3 and 4 it can be seen that the transverse edges of the endless sieve belt 22 are provided with guide straps 22a along the longitudinal extent of these edges. The straps 22a are of an elastic material. According to one embodiment of the present invention, the outer ends of the rollers 18 and 20 are provided with guide grooves within which the straps 22a are held. In this way, the sieve belt 22 is effectively prevented from contracting in a transverse direction which contraction would produce predominantly longitudinal wrinkles in the belt 22 when it is tensioned in a longitudinal direction. In order to longitudinally tension the sieve belt 22, a tensioning device in the form of a setting gear assembly is provided. The tensioning device effectively varies the distance between the rollers l8 and 20. The tensioning device includes a set of bearing blocks 54 mounted at each end of the shafts 42 and 44 of the rollers 18 and 20, respectively. The bearing blocks 54 on each side of the rollers 18 and 20 support spindles 46 and 48, respectively and the spindles 46 and 48 have oppositely directed thread sections which engage with threads within the aligned bores of their respective bearing block set. The spindle 48 can be turned by means of a handwheel 48a. Bevel gears 50 are disposed at the ends of each spindle 46 and 48. The gears 50 mesh with bevel gears 52 of a connecting shaft 53. The spacing between the rollers 18 and 20 is effected by rotating the hand wheel 48a in the appropriate direction depending on whether the spacing is to be increased or decreased.

The tensioning device shown in FIGS. 2 to 4 is particularly suited for endless sieve belts 22 made of bias cut metal wire screens.

The second embodiment of a tensioning device is shown in FIGS. 5 to 7. Here again the guide straps 22a are fastened to the transverse edges of the endless sieve belt 22 along their longitudinal extent. To guide these guide straps, however, guide grooves 60 are provided in tensioning discs 62 which are mounted on the shafts 42 and 44 of the rollers 18 and 20 and rotate therewith. The sieve belt 22 is tensioned in a transverse direction by means of compression springs 64. This can best be seen by reference to FIG. 6.

Elements 64 may also be pneumatic or hydraulic cylinders or the like.

The tensioning device shown in FIGS. 5 to 7 is suited for endless sieve belts with a linear transverse seam, for circularly woven endless sieve belts without a seam and for bias cut endless sieve belts of the type shown in FIG.

4 of the drawings.

It is of course also possible to provide a draining drevice in which the tensioning means of both FIGS. 2-4 and 5-7 are incorporated together along with the helical grooved roller 20.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. A draining device for a paper making machine of the type having a paper slurry-carrying longitudinal sieve travelling over and in engagement with a pair of register rollers spaced from one another in the travelling direction of the longitudinal sieve, one of the re gister rollers being an upstream or first register roller and the other being a downstream or second register roller, comprising in combination:

a. a first end roller having a perforated surface, said first end roller being supported above said longitudinal sieve between said first and second register rollers, said first end roller being situated at a first vertical distance from said longitudinal sieve and being at least 'partially immersed in the paper slurry;

b. a second end roller being supported above said longitudinal sieve downstream of said second register roller, said second end roller being situated at a second vertical distance from said longitudinal sieve, and being out of contact with said paper slurry, said second vertical distance being greater than said first vertical distance; and

c. an endless draining sieve belt trained about said first and second end rollers and being driven with the same linear velocity as said longitudinal sieve, said endless sieve belt having a path of action extending from the location it enters said slurry to a location directly above the highest point of engagement between said second register roller and said longitudinal sieve, said first and second distances being so related to one another that said endless sieve belt extends parallel to said longitudinal sieve along said path of action.

2. A device as defined in claim 1, wherein that portion of said endless sieve belt and the longitudinal sieve which extend downstream of the area of contact of the longitudinal sieve and the second register roller form an angle with one another that is greater than and no more than 10.

3. A device as defined in claim 1, including steam jet generating means disposed between said end rollers above said longitudinal sieve and immediately downstream of the location of contact between said second register roller and said longitudinal sieve for directing a steam jet through said endless sieve belt into a zone immediately above said longitudinal sieve to prevent the formation of subatmospheric pressure in said zone.

4. A device as defined in claim 1, wherein said second end roller is provided on its outer surface with helical grooves starting at its center and extending axially outwardly in opposite winding directions from said center.

5. A device as defined in claim 1, further comprising means for tensioning said endless sieve belt.

6. A device as defined in claim 5 wherein said tensioning means includes guide grooves provided at the axial ends of said first and second end rollers, an elastic guide strap at each transverse end of said sieve belt, each said strap moves in a corresponding guide groove in said first and second end rollers, and setting gear means connected between said first and second end rollers, said endless sieve belt is tensioned by the adjustment of the spacing between said first and second end rollers by said setting gear means and the retention of the distance between said guide straps.

7. A device as defined in claim 6, wherein said endless sieve belt is formed of a bias cut fabric.

8. A device as defined in claim 6, wherein said endless sieve belt is a metal wire fabric.

9. A device as defined in claim 7, wherein said fabric is of bronze.

10. A device as defined in claim 7, wherein said fabric is of stainless steel.

11. A device as defined in claim 5, wherein said tensioning means includes discs which are provided with guide grooves therein, means for displacing said discs in a direction transverse to the movement of the longitudinal sieve, and an elastic guide strap at each transverse end of said endless sieve belt, each strap moves in a corresponding guide groove in said first and second end rollers, said endless sieve belt is tensioned by the adjustment of said discs by said means for displacing.

12. A device as defined in claim 11, wherein said endless sieve belt is of plastic.

13. A device as defined in claim 11, wherein said means for displacing are springs.

14. A device as defined in claim 11, wherein said means for displacing are hydraulic cylinders.

15. A device as defined in claim 11, wherein said means for displacing are pneumatic cylinders.

16. A device as defined in claim 5, wherein said tensioning means includes discs which are provided with guide grooves therein, means for displacing said discs in a direction transverse to the movement of the longitudinal sieve, an elastic guide strap at each transverse end of said endless sieve belt, each strap moves in a corresponding guide groove in said first and second end rollers, and setting gear means connected between said first and second end rollers, said endless sieve belt is tensioned by the adjustment of said discs by said means for displacing and the adjustment of the spacing between said first and second end rollers by said setting gear means.

17. A device as defined in claim 16, wherein said means for producing said transverse displacement are springs.

18. A device as defined in claim 16, wherein said means for producing said transverse displacement are hydraulic cylinders.

19. A device as defined in claim 16, wherein said means for producing said transverse displacement are pneumatic cylinders.

20. A device as defined in claim 1 further comprising a collecting trough for the water splashed from said first end roller, said trough being provided in the region enclosed by said endless sieve belt.

21. A device as defined in claim 20 further comprising a cleaning device for said endless belt sieve, and wherein said collecting trough is disposed to collect the water from said endless belt sieve cleaning device.

22. A device as defined in claim 1, wherein at least said second register roller is provided with an outer surface having openings therein, and has a subatmospheric pressure existing in its interior.

-UNITED STATES PATENT OFFICE CERTIFICATE ()F CORRECTION Patent No. 8 9,4 Dated June 25th, 1974 Inventor(s) il HOlZ It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below In the heading of; the patent, in the Assignees address, change "Ruetlingen" to -Reutlingen-'-. Column 2 line 58 change "adopted g to adapted--.' Column 3 line 55, change "further more" to t Ore--. Column 4 line 29, before "roller" insert en d-; line 55, change "adopt" to adapt--; line 56, change "by" to v -be-'; lines 6l"-65, cancel "To insure. the sieve l0. and insert The vertical distance of the roller 18 from the longitudinal' sieve 10 is smaller than the vertical distance of the roller 20 from the longitudinal sieve l0. In thisv manner parallelism can be ensured between the longitudinal fsieve l0 and that vportion of the sieve belt "22-" that extends from the location where the vertical distance between the roller l8 and the longitudinal sieve 10 is measured to the, location directly above the first point of contact between the register roller 16 and the longitudinal sieve lO.-- Column 5, line 34, delete "assembly". Column. 6 line 24 change "drevice" to device; line 58 change "path of action to portion; line 59, change "it enters said slurry" to' where said first vertical distance is measured--; line 60 change "highest" to -f,irst-; line 65, change "path'of action" tosieve belt po'rtion--. Y v

Signed and sealed this 17th day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. V c. MARSHALL DANN Attesting Officer v v Commissioner of Patents 

1. A draining device for a paper making machine of the type having a paper slurry-carrying longitudinal sieve travelling over and in engagement with a pair of register rollers spaced from one another in the travelling direction of the longitudinal sieve, one of the register rollers being an upstream or first register roller and the other being a downstream or second register roller, comprising in combination: a. a first end roller having a perforated surface, said first end roller being supported above said longitudinal sieve between said first and second register rollers, said first end roller being situated at a first vertical distance from said longitudinal sieve and being at least partially immersed in the paper slurry; b. a second end roller being supported above said longitudinal sieve downstream of said second register roller, said second end roller being situated at a second vertical distance from said longitudinal sieve, and being out of contact with said paper slurry, said second vertical distance being greater than said first vertical distance; and c. an endless draining sieve belt trained about said first and second end rollers and being driven with the same linear velocity as said longitudinal sieve, said endless sieve belt having a path of action extending from the location it enters said slurry to a location directly above the highest point of engagement between said second register roller and said longitudinal sieve, said first and second distances being so related to one another that said endless sieve belt extends parallel to said longitudinal sieve along said path of action.
 2. A device as defined in claim 1, wherein that portion of said endless sieve belt and the longitudinal sieve which extend downstream of the area of contact of the longitudinal sieve and the second register roller form an angle with one another that is greater than 0* and no more than 10*.
 3. A device as defined in claim 1, including steam jet generating means disposed between said end rollers above said longitudinal sieve and immediately downstream of the location of contact between said second register roller and said longitudinal sieve for directing a steam jet through said endless sieve belt into a zone immediately above said longitudinal sieve to prevent the formation of subatmospheric pressure in said zone.
 4. A device as defined in claim 1, wherein said second end roller is provided on its outer surface with helical grooves starting at its center and extending axially outwardly in opposite winding directions from said center.
 5. A device as defined in claim 1, further comprising means for tensioning said endless sieve belt.
 6. A device as defined in claim 5 wherein said tensioning means includes guide grooves provided at the axial ends of said first and second end rollers, an elastic guide strap at each transverse end of said sieve belt, each said strap moves in a corresponding guide groove in said first and second end rollers, and setting gear means connected between said first and second end rollers, said endless sieve belt is tensioned by the adjustment of the spacing between said first and second end rollers by said setting gear means and the retention of the distance between said guide straps.
 7. A device as defined in claim 6, wherein said endless sieve belt is formed of a bias cut fabric.
 8. A device as defined in claim 6, wherein said endless sieve belt is a metal wire fabric.
 9. A device as defined in claim 7, wherein said fabric is of bronze.
 10. A device as defined in claim 7, wherein said fabric is of stainless steel.
 11. A device as defined in claim 5, wherein said tensioning means includes discs which are provided with guide grooves therein, means for displacing said discs in a direction transverse to the movement of the longitudinal sieve, and an eLastic guide strap at each transverse end of said endless sieve belt, each strap moves in a corresponding guide groove in said first and second end rollers, said endless sieve belt is tensioned by the adjustment of said discs by said means for displacing.
 12. A device as defined in claim 11, wherein said endless sieve belt is of plastic.
 13. A device as defined in claim 11, wherein said means for displacing are springs.
 14. A device as defined in claim 11, wherein said means for displacing are hydraulic cylinders.
 15. A device as defined in claim 11, wherein said means for displacing are pneumatic cylinders.
 16. A device as defined in claim 5, wherein said tensioning means includes discs which are provided with guide grooves therein, means for displacing said discs in a direction transverse to the movement of the longitudinal sieve, an elastic guide strap at each transverse end of said endless sieve belt, each strap moves in a corresponding guide groove in said first and second end rollers, and setting gear means connected between said first and second end rollers, said endless sieve belt is tensioned by the adjustment of said discs by said means for displacing and the adjustment of the spacing between said first and second end rollers by said setting gear means.
 17. A device as defined in claim 16, wherein said means for producing said transverse displacement are springs.
 18. A device as defined in claim 16, wherein said means for producing said transverse displacement are hydraulic cylinders.
 19. A device as defined in claim 16, wherein said means for producing said transverse displacement are pneumatic cylinders.
 20. A device as defined in claim 1 further comprising a collecting trough for the water splashed from said first end roller, said trough being provided in the region enclosed by said endless sieve belt.
 21. A device as defined in claim 20 further comprising a cleaning device for said endless belt sieve, and wherein said collecting trough is disposed to collect the water from said endless belt sieve cleaning device.
 22. A device as defined in claim 1, wherein at least said second register roller is provided with an outer surface having openings therein, and has a subatmospheric pressure existing in its interior. 